Autoclave

ABSTRACT

An autoclave, particularly adapted for use as a sterilizer, and in which the functions of steam generation and sterilization are performed in separate steam generating and autoclaving chambers, with provision for controlled delivery of steam from the generating chamber to the autoclaving chamber. A feed water system is also provided incorporating a receptacle for receiving sequential batches of feed water and for heating such batches to a temperature providing a pressure adequate to deliver the batch into the steam generating chamber.

R. B. BLACK AUTOCLAVE July 30, 1974 4 Sheets-Sheet l Ozignal Filed April 4. 1969 R. B. BLACK July 30, 1974 AUTOGLAVE 4 Sheets-Sheet 5 Original Filed April 4, 1969 R. B. BLACK July 3o, 1974 AUTOCLAVE 4 Sheets-Sheet 2 Original Filed April 4, 1969 R B. BLACK AUTOCLAVE July 30, 1974 Original Filed April 4, 1969 4 Smets-Sheet 4 "United States Patent O 3,826,612 AUTOCLAVE Robert B. Black, 2925 Denver St., Corpus Christi, Tex. 78404 Application Aug. 19, 1971, Ser. No. 173,237, now Patent No. 3,717,434, which is a continuation of abandoned application Ser. No. 813,537, Apr. 4, 1969. Divided and this application July 10, 1972, Ser. No. 270,306

Int. Cl. A611 3/00 U.S. Cl. 21--94 2 Claims ABSTRACT OF THE DISCLOSURE The equipment further includes a closure for the autoclaving chamber and means interlocking the operation of the closure with the function of transfer of steam from the generating chamber to the autoclaving chamber. The closure for the autoclaving chamber is in the form of a sliding door mounted adjacent to the access opening into the autoclaving chamber in a manner providing for sealing of the door under the influence of the pressure of the steam introduced into the autoclaving chamber from the steam generating chamber.

This is a division of application Ser. No. 173,237, tiled Aug. 19, 1971 and issuedas Pat. No. 3,717,434 on Feb. 20, 1973, which in turn was a continuation of application Ser. No. 813,537 filed Apr. 4, 1969 and now abandoned.

This invention relates to autoclave equipment and is especially concerned with equipment of this type adapted for use as'a sterilizer, particularly as a sterilizer for instruments and other articles employed in dental and surgical work. Although various features of the invention are applicable to autoclave equipment generally, since most features of the invention are of special applicability and advantage in sterilization equipment, the description hereinafter is primarily related to the use of the equipment as a sterilizer.

Sterilization of surgical equipment and instruments is a basic necessity in hospital routine and in the practice of dentistry and medicine. It is a matter of common knowledge that certain forms of bacteria are not only highly resistant to sterilization, but are also extremely dangerous if not destroyed.

It is `an overall general objective of the present invention to provide euipment affording to the medical, dental and surgical professions a more rapid, convenient, and effective means and system for sterilization than has been provided by any equipment or system heretofore employed.

A number of methods for sterilization have been used or proposed, including employment of both liquid and gaseous chemicals, dry heat, ultraviolet rays, x-rays, as well `as the more common pressurized steam systems. 'Ihe pressurized steam systems as presently known and used, and also various of the other systems are all subject to a number of disadvantages. For instance Avarious of the prior systems are relatively slow in their action. Some detrimentally affect the instruments or equipment being sterilized, and some are not considered sufficiently reliable and effective for safe use, particularly Where it is desired to insure destruction of the spores of certain disease producing' bacteria, such as Clostridia.

Although pressurized steam systems are probably the most rapid and eliicient sterilization systems employed, according to the present state of the steam sterilization art, the full capability and potential of the steam system is not realized, either because of the relatively slow operating or cycling time, or because the equipment is not adapted? to operate at a suiciently high pressure and thus at a' suiciently high temperature to insure the rapid destruc-- tion of all forms of bacteria. One reason for the deficien- 4 cies of the present steam systems lies in the fact that most of# the steam sterilizers employ an autoclaving chamber` which must serve a double purpose by functioning as both steam generator and sterilizing chamber. The requirements of steam generation on the one hand and steriliza-. tion on the other hand are in certain respects antagonistic to one another.

`With the foregoing in mind, it is an important objective of the present invention to provide autoclaving or sterilization equipment in which separate chambers are provided to perform the functions of steam generation on the onehand and autoclaving or sterilization on the other hand.

This has numerous advantages including the fact that=` the sterilization time required can be greatly reduced because the steam generating chamber has a built up reserve which can be delivered instantly at will into the autoclaving chamber as needed for the purpose of autoclaving or sterilizing sucessive batches of instruments or other' equipment to be sterilized. The time cycle required forI sterilization is greatly reduced by this system, since, and:

by way of contrast, a chamber in which both sterilization and steam generation occur necessarily requires a substantial period of time for warm up, i.e., for the heating of the chamber walls and associated structure up to the temperature needed for the steam generation and sterilization.

Another aspect of the currently available steam sterilization systems which has limited the usefulness of those systems is related to the type of closure or door employedto cover the access opening of the steam generating and' autoclaving chamber used. In a typical prior art equip-= ment, the door for the autoclave is a pivoted door which must be fastened with special securing devices designed to draw the door tight against the seal surrounding the accessV opening, and after the sterilization operation is concluded and the interior pressure reduced, such securing devicesy must again be released in order to gain access to the in-4 terior of the chamber for the purpose of withdrawing the instruments or other articles processed.

'Closure equipment of the kind just mentioned is dis-i advantageous because of the time and inconvenience involved in securing and loosening the door holding devices. In addition, the prior door arrangements are disadvantageous because in some cases the securingdevices must work against the pressure within the chamber which normally has a tendency to loosen the seal.

It is another major objective of the present invention to provide an access door arrangement requiring no securto hold the door in lclosed position and further automat-y ically serves to tighten the seal.

With a door arrangement of this kind as contemplated by the invention, it also becomes more practicable to increase the steam pressure used, because the seal is tight- Patented July 30, 1974 cned in accordance with the pressure increase and is not dependent upon mechanical tightening devices. The increase in the pressure and temperature of the steam which is contemplated in accordance with the present invention in turn makes possible shortening the sterilization time. Taking into account the time savings resulting not only from the use of higher pressures and the increased facility of opening and closing the access door, but also resulting from the assignment of the functions of steam generation and sterilization to separate chambers, it is possible according to the present invention to provide a total cycle time for sterilization in the order of one to three minutes in comparison with fifteen to thirty minutes as required by prior known equipment.

It is a further object of the invention to provide separate chambers not only for generation of steam and for sterilization purposes, but also for condensation of steam being discharged from the sterilization chamber at the end of a sterilization operation. The present invention thus contemplates the provision of three chambers, one for steam generation, one for sterilization and one for condensation and storage of the resultant water formed, and it is a further object of the invention to provide interconnections and interlocked controls for these three chambers, functioning in a manner to expedite the overall operation and also to ensure safety and eflciency of the equipment in use.

Still another object of the invention is to provide a novel feed water system for delivering make-up or feed water into the steam generating chamber.

This is accomplished in the preferred practice of the invention by utilizing the water resulting from condensation of steam discharged from the sterilization chamber, whereby the Water employed, such as distilled water is recirculated through the system and thus does not require repeated filling and draining of a treatment chamber as is the case with many prior devices for this general purpose.

It is also an object of the invention to provide a feed water system in which successive batches of feed water are received in a feed water receptacle which is automatically heated as a result of introduction of the water into the receptacle up to a temperature and thus up to a pressure above that prevailing in the steam generating chamber, provision being made for automatic transfer of such a batch of preheated feed water into the steam generating chamber under the influence of the pressure developed in the feed water receptacle.

Another object of the invention is to provide an autoclaving chamber equipped with guide means facilitating the insertion and removal of trays of instruments or articles to be sterilized, the tray and tray supports being arranged so that the trays may readily be at least partially withdrawn from the autoclaving chamber after opening of the access door, with the trays supported in exposed position so as to accelerate cooling of the trays and the contents.

How the foregoing objective and advantages are attained will appear more fully from the following description referring to the accompanying drawings illustrating two embodiments of equipment according to the present invention, and in which:

FIG. 1 is a front elevational view of one form of autoclaving equipment constructed according to the present invention, this view showing the access door for the autoclaving chamber in open position;

FIG. 2 is a top plan view on a larger scale, showing the equipment of FIG. 1, with certain parts broken away and shown in horizontal sections, as will further appear;

FIG. 2a is a fragmentary view of certain parts, as will be explained;

FIG. 3 is a front sectional elevation of the equipment of FIGS. 1 and 2, this view being on the scale of FIG. 2 and also having certain parts broken away and others shown in vertical section;

FIG. 4 is an isometric view of the autoclaving or sterilizing chamber of the embodiment of FIGS. 1, 2 and 3,

having an access door arrangement according to the present invention, parts of the door and of the mounting therefor being broken off and shown in section;

FIG. 5 is a diagrammatic view of the equipment of FIGS. 1 to 4, illustrating the steam generating and condensing chambers in outline and illustrating in vertical cross section the shape of the autoclaving chamber, this view including a diagrammatic represenation of the piping, valve and control arrangements and including also a schematic diagram of the electrical control circuits employed;

'FIG 6 is a front partial sectional view of another form of equipment according to the invention; and

FIG. 7 is a side view of portions of the equipment shown in FIG. 6, the steam generating and autoclaving chambers being shown in vertical section, as indicated by the section line 7-7 on FIG. 6.

Referring first to the embodiment illustrated in FIGS. l to 5 inclusive, attention is first directed to FIG. 1 which shows an overall front elevation of the equipment as enclosed in a casing and with the various controls exposed at the front panel. Here it will be seen that the front casing wall 8 is provided with an aperture in the upper central portion of the equipment in general registry with the access opening to the interior of the autoclaving or sterilization chamber. The door 9 for the access opening is shown in open position, so as to expose three trays 10 positioned in spaced superimposed relation. TheseV trays may be inserted into and withdrawn from the autoclaving chamber through the aperture in the front wall of the casing as will readily be apparent.

The front panel 8 of the equipment shown in FIG. 1 also serves to mount various gauges, instruments and controls as will be mentioned as this description proceeds, and the entire unit is adapted to be supported by rubber feet 11 which project downwardly from the base 12 of the casing or support structure for the various parts of the apparatus.

Toward the left of the front panel in FIG. 1 there appears a gauge glass or window 13 through which the level of water in the steam generating unit to be described may be observed.

From FIGS. 2 and 3 it will be observed that the casing includes not only the front and bottom walls 8 and 12 but also side walls 14 and 1S, back wall 16 and top Wall 17. These casing walls may be made up in any convenient manner as by assembling separate metal sheets. The interior of the casing is also here shown as divided by two upright partitions 18 and 19 which in effect serve to divide the interior space into three compartments each adapted to receive one of the operating chambers of the equipment. Thus, toward the left of the unit the steam generating chamber 20 is positioned between the casing wall 14 and partition 18. Between the partitions 18 and 19 the autoclaving chamber 21 is received, and between the partition 19 and the side wall 15 the condenser chamber 22 which serves as a Water reservoir, is received.

As above noted the sterilization or autoclaving chamber 21 is provided with an access opening in its front end, as indicated generally at 23 in the perspective view of FIG. 4. This autoclaving chamber is of generally rectangular shape, -being closed at its side, bottom, top and rear end, as is clearly shown in the drawings. Along the inside of the two side walls of the autoclaving chamber grooved guides 24 are provided in pairs, each pair of guides being adapted to receive the marginal flanges which are provided at the upper side edges of the trays 10.

Near the bottom of the autoclaving chamber is a perforated partition or plate 25', spanning the chamber from one side wall to the other and extended throughout the length of the chamber. A centrally located steam inlet pipe 26 passes through the bottom wall of the autoclaving chamber and terminates below the perforated plate 25, this pipe 26 serving as the inlet or supply line for steam delivered from the steam generating chamber into the atocla'ving chamber. The central area of the plate 25 justabovethe inlet 26 isimperforate, as `indicated at 27 (seo FIGS. 2 and 3), and'this aids in distributing the incoming steam in the space below the perforated plate 25. 'I'heperforations then serve to distribute the incoming steam throughout the entire volume of the autoclaving chamber.

ySince steam is to be delivered into the autoclaving chamber, it is not necessary for that chamber to be deeigned" to function as a steam generator. According to the invention the steam generation function is assigned to the" steamy' generating chamber `2t) which comprises a receptacle 'or tank of generally rectangular shape, closed at all sides. Transverse braces or stay bolts 2S are extended between the relatively large area side walls of the chamber inprder to provide adequate strength to resist the internal pressure, even where the chamber is constructed of relatively thin metal sheet.

the bottoml ofthe steam generating chamber 20, prefefrably` projecting through Vthe'baclc 'wall near the bottom wallfis an electrical heating element 29, this element advantageouslyfbeing of -,shaped form and having electrical connections such as indicated at 30 (FIG. 2) extended frorn'l its ends to the current supply and control system. The offtake of steam from the chamber 20 is effected by the upwardly open oftake or discharge pipe 31 which extends downwardly through the generating chamberto a point near the, bottom and then passes through the inner sidewall ofthe chamber Vin a horizontal run as indicated at A3,2 in FIG. 3'.,The portion of this steam offt`a=ke indicated lat l32` connects with a solenoid operated control L valve 33 which in` turn delivers the steam through pipe 34 to the inlet pipe 26 of the sterilizing chamber 21 ashplainly appears in the drawings. i v

At the conclusion of agsterilizing operation, steam is dischargd from the sterilizing chamber 21 through the connection' 26 which previously served Vas the inlet connection, this exhaust steam being delivered through the pipe 35 andthe solenoidoperated valve 36 to the connection 37 which extends into the bottom of the condenser chamber -22. The condenser chamber serves as a reservoir for feed water to be returned to the steam generating chambenand` a helical condenserA pipe 38 disposed within the water in the condenser chamber receives the exhaust steam from the pipe 37 and, during the upward ilo-w through the` coil ,38, the exhaustv steam is caused to condense, the water ultimately discharging from the upper open end 39 of the condenser pipe into the. interior of the condenser chamber, so that the water thus returns to the feed water system for Yultimate return tothe steam generating chamber.

-As will-be explained in greater detail in connection with FIG.l 5 herebelow, the valve 36 is closed when valve 33 is opened to admit lsteam into the autoclaving chamber.-Conversely the valve 33 is closed when the valve 36 isopened `to deliver the; exhaust steam from the autoclaving chamber into the condenser.

Another connection is provided between the autoclaving chamber21 and the condenser chamber 22. This connection, indicated at 40 serves to deliver air being displaced from the top of4 the autoclaving chamber at the time when steam is admitted .into the 'bottom of that chamber. The pipe 40 is provided with a temperature responsive valve 41 which closes vautomatically upon appreciable rise in temperatureinconsequence of some steam owing through the pipe 40 as the autoclaving chamber is being charged. The connection of this pipe 40 with the condenser chamber 22 provides for return to the feed water reservoir of any liquid or condensate escaping from the lautoclaving chamber through the pipe 40.

' The Vfeed water system includes a receptacle 42 located below the level ofthe condenser chamber so that water willflow by gravity from the feed water reservoir into the receptacle 42. This flow may occur from the outlet connection in the bottom of the condenser chamber, through a ilexible section of pressure resisting tubing 43 extended through a side wall of the feed water receptacle 42. The flexibility of the connection 43 permits vertical movement of the feed water receptacle 42, and it will be noted that the receptacle 42 (see FIG. 2a) is mounted by means of a pivot 44 providing for upward and downward movement of the receptacle 42. A spring 45, which may be made adjustable, normally holds the receptacle 42 in its upper position, but will yield and permit downward movement of the receptacle when the receptacle is nearly filled with water entering through the connection 43. A check valve 46 is located in the connection 43 and serves to prevent upward ow of steam or water from the receptacle 42 into the bottom of the condenser chamber.

A U-shaped electrical heating element 47 is positioned in the receptacle 42 and serves to heat the water therein and thereby develop pressure by means of which the batch of water entrapped in the receptacle 42 may be returned to the steam generating chamber 20. A connection 48, desirably formed of llexible tubing so as to ac commodate the vertical motion of the receptacle 42, extends from the receptacle to the bottom of the steam generating chamber, this connection also being provided with a check valve 49 adapted to block flow in the direction from the steam generating chamber back into the receptacle 42.

Before considering the control system and operating arrangements in connection with the diagram of FIG. 5, particular attention is now directed to the access door for the autoclaving chamber, and the mounting of that door in association with the access opening of the autoclaving chamber. The arrangement of these parts can best be understood from inspection of FIG. l4. Here it will be seen that the access door 9 comprises a flat plate which is vertically movable. Upward motion, as by lifting on the insulated handle 50, serves to close the access opening, and downward motion opens the access opening, as will readily appear from FIG. 4.

The door mounting structure comprises an inner flat plate 51 having an opening 52 in registry with the access opening into the autoclaving chamber, and the inner side of this plate is preferably welded to the walls of the chamber itself. A similar outer plate 53 having an opening 54 in registry with the access opening is positioned in parallel relation to the plate 51, the two plates being held in separated positions by the apertured spacing plate 55 which extends around the periphery of the other plates. Gaskets between plates of approximately 1,52 of an inch thickness result in about 1/16 of an inch clearance space between the sliding door and the plates between which it slides. At the inner side of the outer plate 53, surrounding the aperture 54 therein, and thus surrounding the region of the access opening into the autoclaving chamber, the plate 53 is provided with a groove for receiving a sealing ring 56, formed, for example, of rubber. This sealing ring is adapted to be engaged by the outer face of the door 9 when the door is closed. In the absence of pressure within the autoclaving chamber 21, the door preferably has sucient clearance between the plates 53 and 51 and also between the sealing ring 56 and the plate 51 so that by the action of gravity on the door, the door will drop down to the lower or open position. On the other hand when it is desired to carry out a sterilization operation, after the articles or instruments are inserted into the chamber, the door is lifted to its closed position and steam is then caused to enter the autoclaving chamber, and just as soon as some steam pressure develops, that pressure will act upon the door to push the door outwardly against the sealing element 56 and this will retain the door in its closed position automatically against the action of gravity. Moreover, this action will result in increasing the tightness of the seal with increase in pressure within the autoclave.

Still further, at the termination of a sterilization operation, when the steam is being exhausted from the autoslave, when the pressure drops to a level approaching atmospheric pressure, the door will automatically drop open, without requiring the attention of any attendant and without manually loosening any securing device.

Turning now to the diagram of FIG. 5, it is first to be understood that it is contemplated according to the invention that the steam generating chamber remain heated and in condition serving as a reservoir for pressurized steam at all times when it is expected that sterilization operations may desirably be performed. For example, it is expected that in the use of the sterilizer during the course of a day, the equipment will be powered and the steam generating chamber will remain heated throughout the day so that a supply of steam is always available for instant use whenever it is desired to effect a sterilization operation. In situations where it may be desired to sterilize instruments at any time during the day or night, for instance in a hospital, the equipment may be powered and the steam generating chamber charged at all times.

Having in mind the foregoing contemplated aspects of the operation, the equipment may be pluged into a power supply line, for instance a 120 volt 60 cycle power supply line and the equipment may be turned on and off, by means of the master switch 57 shown not only on FIG but also on the control panel in FIG. 1. This switch is in one side of the power supply comprising the lines 58 and 59. A connection 60 extends from the line 59 to one side of the heater element 29 in the steam generating chamber. The other side of the heater element 29 is connected by a wire 61 with one side of an adjustable pressure responsive switch 62, the other side of that switch being connected as indicated at 63 with the side of the line 58 through the master switch 57. A steam connection 64 is extended from the steam generating chamber to the pressure switch 62 and acts to open switch 62 when the pressure rises to a pedetermined level, which point may be adjusted by setting the switch 62. The connection 64 is also employed to operate a pressure gauge 65, the switch 62 and the gauge 65 both being shown in FIG. 1 as well as in FIG. 5.

Signal lights are provided so as to indicate whether the heater in the steam generator is on or off. These lights desirably include a red light 66 connected at one side to the wire 61 and at the other side by a wire 67 with the terminal of the heater 29 with which wire 60 is associated. Therefore when switch 62 is closed, thereby energizing the heater element 29, the red light is turned on. On the other hand when switch 62 is open, the red light 66 is deenergized but the white light 68 will be lighted because of current supplied at one side through the connection 63 and at the other side through the connnection 61, through the heater element 29 itself, and the connection 60 to the opposite side of the power supply.

The solenoid operated valve 33 for delivering steam from the generating chamber to the sterilizing chamber 21 is controlled by a circuit including the wire 69, microswitch 70, wire 71 and the timer switch 72, the opposite side of which is connected with the wire 63 and 'thus with the side 58 of the power supply in which the master switch 57 is inserted. The other side of the solenoid operated valve 33 is coupled as indicated at 73 with the Wire 74 extending to the Side 59 of the power supply. Therefore, with both the microswitch 70 and the timer switch 72 closed, the solenoid operated valve 33 is actuated to open the steam supply line to the autoclaving chamber. At the same time the solenoid operated valve 36 is actuated to close the exhaust steam line 35-37, both of these solenoid operated valves (33 and 36) being controlled by the same timing circuit. For the purposes just mentioned the valve 33 (normally closed type) is arranged to open when its solenoid is energized, and the valve 36 (normally open type) is arranged to open when its solenoid is de-energized.

The timer controlled switch 72 is adapted to be Set so as to close the circuit for any desired interval of time, for instance two minutes, and provided the microswitch 70 is at that time also closed, the steam inlet valve 3 3 will remain open and the steam exhaust` ,valve 36 will remain closed until the set time runs out. This will break the circuit at the timer switch in consequence of which the steam supply valve 33 is closed and the exhaust valve 36 is opened. v

It is now pointed out that the actuating elementfor the microswitch 70 is positioned in the path of the door 9. Thus, as best seen in FIGS. 2 and 3, the microswitch 70 is provided with an arm 75 carrying an actuating pin v76 positioned to be engaged by the upper edge of the door 9 when the door is lifted to close the access opening. In operation, the timer will be set to a predetermined setting and the'n the door is manually raised to the closed position and this immediately actuates the microswitch 70 to com# plete the circuit which will open the supply valve 33 and close the exhaust valve 36. At the end of the cycle of operation established by the time switch 72, the steam supply valve 33 will close and the exhaust valve 36 will open, and after dissipation of the pressure in the auto-4 claving chamber, the door 9 will automtically drop down to the open position, thereby opening the microswitch 70, which will prevent unintentional readmission of steam into the autoclaving chamber should timer actuated switch be again turned on until the door is again manually lifted to its closed position.

During the interval of initail entrance of steam into the autoclaving chamber the air in the chamber will be exhausted through the pipe 40 as above mentioned and through the temperature responsive valve 41, until the temperature of that valve rises appreciably, which will thereby shut the valve and thus maintain the desired pressurized condition within the autoclaving chamber. The pipe 40 is further used as a source of steam for the reading of temperature by the temperature gauge or thermometer 77 (see also FIG. 1) and, in order to ensure accuracy of reading of this thermometer, a bypass 78 is provided around valve 41, this bypass being provided with an adjustable needle valve 79 by which the bypass may be choked down to a small bleed port.

The pressure within the sterilizing chamber is indicated by a pressure gauge 81 provided on the panel as will be seen from FIG. 1, this gauge being connected by small tube to pipe 40.

The heater element 47 in the receptacle 42 of the feed water supply system is connected with one side of the power supply by means of the wire 82 in which a control switch 83 is provided (see also FIG. 1). The other side of the heater 47 is connected through microswitch 84 with a wire which in turn is coupled with wire 74 leading to the other side 59 of the power supply line. The actuating element of the microswitch 84 is positioned to be engaged by the receptacle 42 when it has moved to down position by weight of the water from the feed water reservoir in the bottom of the condenser chamber 22. This microswitch is adapted to close the circuit when the receptacle 42 moves downwardly and to open the circuit when the receptacle 42 is lifted by the springs 45. Therefore, when the switch 83 is closed and water flows downwardly from the condenser chamber 22 into the receptacle 42, the consequent downward motion of the receptacle 42 will activate the heater 47 and upon the attainment of a temperature and pressure somewhat above those prevailing in the steam generating chamber 20, the charge of water in the chamber 42 will be delivered through the connection 48 and the check valve nual switch 83, a switch operating automatically under the influence of the level of the water in the steam generating chamber say be employed to automatically activate the heater in the water receptacle 42, and thereby provide for introduction of additional water into the steam generating chamber whenever the level of the water drops below a predetermined point.

The various chambers of the equipment and other parts of th apparatus, especially those parts coming in contact with the steam or water, are desirably formed of corrosion resistant metal such as stainless steel. The autoclaving chamber is also desirably provided with appropriate lagging or insulation such as indicatedat 86. Similar insulating material 87 may be provided around at least certain of the walls of the steam generating chamber 20. On the other hand it is desirable to maintain the condenser chamber relatively cool, and for this purpose air circulation apertures may be,v provided in the casing walls in the vicinity of the condenser chamber, for instance in the bottom wall or floor as'indicated at 88 in FIG. 3 and also in the top wall 17 as indicated at 89 in FIG. 3.

The condenser chamber is of course a low pressure chamber, preferably substantially atmospheric pressure anda removable lid or cover 90 (see FIG. 3) may be provided for the purpose of introducing make up water, although, because of the circulation system established -by the equipment, make up water need be introduced only infrequently.

Turning now to the embodiment illustrated in FIGS. 6 and 7, it is to be noted that the autoclaving chamber and door arrangement of this embodiment are identical to those employed in the first embodiment. However, instead of arranging the steam generating chamber to the left or to a side of the autoclaving chamber 20, in the embodiment of FIGS. 6 and 7, the steam generating chamber is positioned below the autoclaving chamber, as is indicated at 20a. Moreover, instead of positioning the solenoid valves 36 and 33 below the autoclavingchamber, `these valves are positioned either between the autoclaving chamber and the condensing chamber, as clearly appears in FIG. 6, or between the autoclaving chamber and the left wall 14 (FIG. 3) or behind the steam generator 20a. Connection 32a serves to deliver steam from the generating cham-ber to the solenoid valve for controlling admission of steam into the autoclaving chamber, and connection 26a runs from the solenoid valves to the autoclaving chamber and serves both for steam admission and for exhaust of steam, in the latter event the steam being directed through valve 36 to the connection 37a which leads to the condensing coil provided in the condenser chamber 22 which is located in relation to the autoclaving chamber in the same general arrangement as in ,the first embodiment.

The disposition of the steam generating chamber below the 'autoclaving chamber, preferably with a single partition *fwall such as indicated at 21a in FIG. 7 serves an important function in the embodiment of FIGS 6 and 7. During the interval of sterilization, a substantial amount of steam condensation normally occurs on the upper, back and side walls of the autoclaving chamber, and this condensation flows down the walls and in the arrangemefltit just described when this condensation reaches the common partition 21a between the autoclaving and steam generating chambers, the heat in the generating chamber will be transferred through the wall 21a to the accumulating moisture, thereby revaporizing that water. This re vaporization process results in substantial reduction of water consumption per sterilization cycle.

It will be understood that control systems of the kinds' fully described above with reference to the -rst embodiment, and particularly with reference to FIG. will be employed in the embodiment of FIGS. 6 and 7 and also that a feed water system of the kind described above may likewise be utilized in the embodiment of FIGS. 6 and 10 7. A gauge I13a indicating the water level in the generating chamber 20a may also be provided.

The use of the feed water receptacle 42 and the electrical heating system providing for the delivery of batches of feed water from the receptacle to the steam generat ing chamber is of special advantage where it is desired to maintain continuous operation of the sterilizer equipment, as, for example, in hospital use. However, in equipment intended for use throughout only a portion of the day, for instance from 9:00 am? to 6:00 p.m., as in the office of a dentist or doctor, the equipment may be somewhat simplitied. For example, the feed water rceptacle 42 and its heater, with the control system provided, as described above with particular; reference to FIGS. 3 and 5, may be omitted, and the connection 48 may be directly coupled -with the lower Vpart of the condensing chamber 22. In this variant, upon shutting 0E the power supply (as by the shut oil. switch 57 the temperature and pressure in the steam generating, chamber will drop in the course of a few hours. The temperature drop will be sufficient to lower the pressure to a value below atmospheric pressure, in consequence of which the water present in the condensing chamber 2&2 will automatically be drawn into the steam generatinglchamber, so ythat when the power switch 57 is again closed, for instance at the commencement of the next day'sf` use of the equipment, adequate water is present in the steam generating chamber to continue the operation through a substantial number of sterilization cycles.

It will be understood that other forms of feed water pumps or an injector could be used to transfer water from the condenser chamber to the steam generating chamber.

I claim:

1. Autoclave equipment comprising an autoclaving chamber for receiving articles to be autoclaved, steam supply means including a separate closed pressurized steam generating chamber having heating means, a supply line interconnecting said chambers and having a steam supply valve for admitting steam from the generating chamber into the autoclaving chamber, steam exhaust means including an exhaust line extended from the autoclaving chamber and having an exhaust valve for exhausting steam from the autoclaving chamber, a condensing chamber connected with the exhaust line and receiving the exhaust steam therefrom, the condensing chamber being open to atmospheric pressure, a connection between the condensing and generating chambers for delivering condensate from the condensing chamber to the steam generating chamber, said connection having a check valve therein providing against ow from the generating chamber into the condensing chamber but providing freedom for ow from the condensing; chamber to the generating chamber, said connection being normally open except for said check valve, and control means for the heating means providing for cooling f he'igenerating chamber and thus for condensation of steam therein with accompanying decrease inlpressure and resultant delivery of condensate from thevl condensing chamber into the steam generating chambier under the influence of atmospheric pressure in the condensing chamber.

2. Autoclave equipment comprising an autoclaving chamber for receiving articles to 'be autoclaved, steam supply means including a separate closed pressurized steam generating chamber having heating means, a supply line interconnecting said chambers and having a steam supply valve for admitting steam from the generating chamber into the autoclaving chamber, steam exhaust means including an exhaust line extended from the autoclaving chamber and having an exhaust valve for exhausting steam from the chamber, a water reservoir open to atmospheric pressure and having a connection extended between said reservoir and the generating chamber for delivering water to the steam generating chamber, said connection having a check valve therein pro-- -1 1 vildingagainst.flowrffrernthe generating chamber to. the reservoir bt vproviding freedomlfor ow .from thereservoir. t9 thevgenerating chamber, said connection -being I lQrmallyi lpenexcept for s aid check valve, and controly means. 4for the heating. mensproviding for cooling of the,generating...chamberfand thus for condensation rof sgearn. therein with accompanying decrease in` pressure ar '1d2resu1`tan t.,delivery`of water frQm the reservoir into the steam .generating chamber under ,the inence 0f atmospheric; pressure in the reservoir.

v fn References Cited UNITED STATES PATENTS 2,412,775 12/1946 Jeffords 21-94 UX 2,526,974 10/1950 Sehipanski 21-98 2,639,675` 5/1953` Williams 21-94 UX 

